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coma

Depressed consciousness to the extent that the patient is unresponsive to noxious stimuli. (also see arousal) Etiology: - diffuse insults to cerebral hemispheres* - damage to reticular-activating system - combination of cerebral hemisphere & brainstem dysfunction - structural lesions, toxic, metabolic & infectious causes - also see differential diagnosis of coma * unlateral hemispheric lesions alone do not cause coma [2] Pathology: 1) persistent vegetative state follows a period of coma 2) unaware of self or environment 3) no purposeful response to stimuli, noxious or otherwise 4) continuation of sleep-wake cycles & brainstem function Clinical manifestations: - unaware of self & environment - no response to noxious stimuli - sleep-wake cycles & brainstem function may remain - also see persistent vegetative state Physical examination: 1) Glasgow coma scale 2) pupillary size 3) ocular motility a) doll's eyes b) cold calorics c) horizontal disconjugate gaze 1] cranial neuropathy 2] ipsilateral cerebral hemispheric lesion 3] ipsilateral pontine lesion 4] contralateral thalamic lesion d) vertical disconjugate gaze - brain stem lesion e) nystagmus suggests epileptiform activity Laboratory: 1) serum chemistries a) electrolytes b) serum glucose c) serum Ca+2 d) urea nitrogen e) plasma ammonia (NH3) f) osmolality 2) urine toxicology 3) lumbar puncture & CSF examination - suspected meningitis or subarachnoid hemorrhage (normal neuroimaging) Special laboratory: - electroencephalogram (EEG) to exclude non-convulsive status epilepticus Radiology: 1) urgent computed tomography (CT) to rule out hemorrhage, mass lesion 2) magnetic resonance imaging (MRI) Differential diagnosis: - locked-in syndrome - quadriplegic, mute, preserved vertical eye movements - nonconvulsive status epilepticus, toxic, metabolic & infectious disorders - no focal neurologic signs, meningism or fever - meningitis, meningoencephalitis, subarachnoid hemorrhage - meningismus, no focal neurologic signs - stroke, hemorrhage, tumor, abscess - focal neurologic sign(s) - brain death: coma, absence of brainstem reflexes, apnea Management: 1) establish stable vital signs - airway, breathing, circulation 2) administer urgent therapy for potentially reversible causes a) glucose plus thiamine 100 mg IV - fingerstick for blood glucose can obviate the need [2] b) naloxone if opioid overdose is suspected [2] c) consider flumazenil - avoid in patients with seizure disorder 3) endotracheal intubation for airway protection 4) stabilize neck if evidence of trauma - evaluate cervical spine 5) prognosis a) patients with drug-induced or metabolic coma have the best prognosis: complete recovery is not uncommon b) diffuse anoxic encephalopathy & focal structural disease have poorer prognosis c) the most sensitive early (48 hours) markers of poor outcome after cardiac arrest (no sedation) are: - no pupillary response or corneal response - absence of motor response to pain - burst suppression pattern on electroencephalogram [4,5] d) death or severe disability in > 95% of patients with with abonormal brainstem responses or absent motor responses by day 3 e) patients with non-traumatic coma who do not improve within 1 month are unlikely to regain consciousness; beyond 3 months, recovery is extremely rare f) overall, 15% of patients with non-traumatic coma have a satisfactory recovery g) patients with traumatic coma are more likely to survive than patients with non-traumatic coma h) after 10-14 days, patients may transition into vegetative state i) patients with traumatic coma are more likely to regain consciousness despite prolonged coma lasting several months j) also see outcomes of comatose patients after CPR 6) consider organ donation in those patients who meet criteria for brain death

Related

differential diagnosis of coma Doll's eye phenomenon (oculovestibular reflex) Glasgow coma scale (GCS) outcomes of comatose patients after cardiopulmonary resuscitation (CPR) persistent vegetative state

Specific

diabetic coma hepatic coma hyperglycemic-hyperosmolar syndrome; hyperglycemic-hyperosmolar nonketotic coma (HHNC)

General

disorder of arousal; lack of awareness; impaired consciousness loss of consciousness (LOC)

References

  1. Clinical Anatomy Made Ridiculously Simple. Stephen Goldberg, MedMaster Inc, Miami, 1995
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 19. American College of Physicians, Philadelphia 1998, 2006, 2021 - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  3. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 130-133
  4. Booth CM, Boone RH, Tomlinson G, Detsky AS. Is this patient dead, vegetative, or severely neurologically impaired? Assessing outcome for comatose survivors of cardiac arrest. JAMA. 2004 Feb 18;291(7):870-9. Review. PMID: 14970067
  5. Wijdicks EF, Hijdra A, Young GB, Bassetti CL, Wiebe S; Quality Standards Subcommittee of the American Academy of Neurology. Practice parameter: prediction of outcome in comatose survivors after cardiopulmonary resuscitation (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2006 Jul 25;67(2):203-10. PMID: 16864809 Review.
  6. NINDS Coma Information Page https://www.ninds.nih.gov/disorders/all-disorders/coma-information-page